In the pursuit of power, mankind has often followed the path of war after diplomacy yielded no results. In this regard, countries have always looked for ways to tip the scales of power in their favor: from the invention of the first trebuchet to the use of the atomic bomb, the technological advancements made in warfare have been mind-blowing. Even though some of these advancements have often led to the bettering of societal technologies, there have always been tragic costs associated with wars – the loss of innocent life. In recent wars, there has been a climb in these types of deaths. To battle the loss of life associated with stray bullets or inaccurate shootings, technological advances have been researched to mitigate this growing trend.
DARPA, the Defense Advanced Research Projects Agency, has recently unveiled a new type of bullet that would decrease the inaccuracy of bullets fired. The process of controlling this aspect would mitigate both the loss of innocent life as well as target the not-so-innocent groups during times of war. Dubbed the EXACTO bullet (extreme accuracy tasked ordinance bullet), it would be capable of adjusting its flightpath to the specifications described by the shooter. The controlling variable in this scenario would be the flight path of the bullet. If the flight path of a bullet could be pre-determined, it would both increase the chances of success in a mission as well as decrease the chances of civilian casualties. A good operating range would then be the bullet finding its appropriate mark; a bad operating range would be hitting anything besides its appropriate mark. Since the saving of innocent life is always paramount in any given situation, the control of this specific variable would be very critical to the operation.
To control this application, several factors would have to be taken into account. To test the potential of controlling the accuracy of a bullet, DARPA has looked into incorporating controlling mechanisms into 50 caliber bullets. These large caliber bullets are typically associated with long range sniper rifles that rely on large amounts of precision and accuracy due to the long distance that usually exists between the shooter and target (up to 1500m). Although bullets are fired from these rifles at roughly 800m/s, several factors come into play at such extreme lengths that can alter its path. Some possible factors include wind speed, humidity, temperature, elevation above sea-level, air resistance, muzzle velocity, and gravity. Since it is impossible to control disturbance factors, such as wind speed or temperature, the technology within and on the bullet would work to counteract these factors, or would be constantly fed through some controlled process to account for these variables. A control system that could compensate for these factors would minimize the human error that arises from shooting at long distances.
Moving targets pose the largest challenge for shooters. In most scenarios, snipers will wait until the target is stationary before taking their shot. If that controlled variable cannot be achieved, a new decision comes into play: the anticipation of where the target will be at a given time in the future. Regular bullets do not change their trajectory once released from the barrel, so if the target moves, the bullet could miss the target and hit someone else who wandered unwittingly into its path. At such great distances, the chance of this happening is higher than for close-up shots, so snipers must take enough time to set up before taking a long-distance shot. Once the shot is taken, the shooter’s position becomes compromised, and the opportunity to hit the target has passed. “Locking” onto the target and having the bullet change trajectory in response to the target’s motion, or even incorrect aim, could significantly increase the number of bullets that reach their targets. DARPA’s team has been able to correct for this by controlling the bullet to change trajectory in response to the moving target.
The bullet uses a feedforward response system, meaning it will detect the change in location of its target while both are in motion, and it will alter its direction in order to re-focus on its target. DARPA has not unveiled its full secrets surrounding the technology of the bullet; however, the basic mechanism for the path change is known. It does so by following a laser-designated mark, altering its flight path by moving small fins up to 30 times a second, to adjust for changes in position. With this new technology, targets should be hit more often, allowing soldiers to fight more effectively than ever. Similar technology has proven efficient in smart bombs; however, the challenge here was developing electronics that would be small and capable enough to fit inside the base of the bullet. Additionally, not only would the bullets be more accurate, but they would also allow for shots to be taken more quickly. The bullet will be able to account for inaccuracies in aim, which will allow the sniper to be slightly less accurate and much faster at taking a shot. Their ability to move in and out of position quickly will reduce the risk they pose to themselves and their unit by compromising their position.
This YouTube video demonstrates and explains the target-locking technology:
https://www.youtube.com/watch?v=PjdEweHYxEk
Some sample moving-targets are shown in this YouTube video:
https://www.youtube.com/watch?v=YoOaJclkSZg
Large leaps in bullet technology have already been made. Over the course of centuries, bullets have progressed from round, spherical shapes, to the elongated egg forms with a pointed end, which are used today. This step significantly cut down on the air resistance the bullet encounters, leading to the increase in the total travel distance of the bullet through the air (from 100 yards when using Civil War muskets to roughly 7,000 yards for the sniper rifles used today). With small changes having such significant effects, all factors should be considered when attempting to make an improvement towards a certain goal. To improve accuracy, the factors that need to be controlled the most are wind speed and the location of the target. Large gusts of wind can derail a bullet from its flight path, and the flight path of an ordinary bullet does not change based on movement of the target. Because of the tiny fins located on the shell of the bullet, obstacles, such as these, could be overcome with a slight adjustment relayed from the laser-marked target to a guidance system located in the bullet. Since controlling these outside factors is impossible, the next step forward would be to counteract these effects by inserting a feedforward loop. A feedforward loop works by monitoring disturbances in the path of the bullet before it reaches its intended target. The control system will monitor the wind speed and location of the person, and if either of these change, the controller will alter the path of the bullet before it hits the person. If the system works properly, the target will be hit every time.
Moving forward, many challenges arise that make the design of this system difficult, and limitations require alternative ideas. Since the bullet would still be travelling at such high velocities, any type of system correction would have to be done in less than three seconds (taking into account the distance to the target is roughly 2400 meters away). Because of this limited window of correction, a fail-safe should most likely be installed, which would cause the bullet to self-destruct or stop mid-flight.
With improved technology, the country will grow stronger. War will be completed more efficiently, and more soldiers will return home quickly and safely. Fewer civilians will be lost in the process. These bullets could provide the technological advantage needed to come to a quick resolution regarding political conflicts while minimizing the interaction of those not directly involved.
The war does all the harms but no benefits. It destroys lives which are the most treasurable things on earth. The purpose of the technologies should never be to win a war, but to stop a war. This specific technology can be used to hit terrorism. In the mundane life, it can benefit the weapon lovers who would love to try out new weapons with fascinating technologies. For myself, I am really interested in this technology. If it is available, I will definitely try it in the shooting range. In the standpoint of a soldier, this technology can greatly increase their accuracy of hitting a target and maybe can save their lives in the battlefield. For a sniper, it can increase their accuracy and decrease the time to aim the target.
Controlled variable, in this case, is the flight path of the bullet. It can be controlled by the manipulated variables which are the fin adjustment. An amount of disturbance variables is present to influence the flight path of the bullet, such as the ambient conditions (i.e. wind speed, temperature, atmospheric pressure, gravity, and humidity), and the also the way how the shooter shoots the gun (i.e. the way the shooter aims the target). Moving targets can be another disturbance variable which requires significant path change of the flight. Since trajectory is not changed after the bullet leaves the gun, moving targets can be hard to be aimed at.
A feed forward system is used in this case since there is only one chance to achieve the goal and therefore the feedback system cannot be used in this case. The bullet adjusts itself to the disturbance variables while sensing the motion of the target. However, there is a physical limitation of the fin adjustment. If the bullet is too off from the target, even the maximum adjustment by the fin cannot make the bullet hit the target. A fail-safe control is likely to be installed as mentioned in the blog. The bullet can destroy itself if it cannot hit the target. Accordingly, even if the bullet will miss its target, the target does not detect the existence of the bullet. With the combination of the self-adjusting and fail-safe controls, the bullet can always hit the target successfully.
A proportional controller is not likely to be used since adds offset in this system which seeks for significant accuracy. A PID controller cannot be used since there are too many disturbances giving constant changes. Accordingly, a PI controller is likely used. The can be set to be minimum and the can be set to be maximum as is not too close to the of the sensors in order to make a quicker response and a more stable process.
If this application were successful and was to be used in a war, the country with this technology could have a better chance of winning the war without too many casualties. However, in another standpoint, the country without this technology could have more casualties. Again, the purpose of this technology should never be to win a war, but to stop a war.
The EXACTO bullets being developed by DARPA are a sure sign of the ever-evolving weapons landscape. Researching these bullets and watching them in videos is a frightening experience. As was probably said about all other major weapons innovations in history, this has the potential to change the battlefield for a long time.
This technology is very practical. Smart bullets that can adjust their path based on weather conditions, poor aim, or moving targets can be incredibly effective if they are tuned properly. The implementation of these bullets would greatly increase the distance from which snipers can accurately shoot. Although the article mentions that maximum distance for a sniper rifle bullet is currently 7,000 yards, an expert sniper, perfect conditions, and a stationary target would be prerequisites for an accurate shot. The utilization of these smart bullets would theoretically eliminate those needs.
Hopefully, this technology would only be used by the United States military. Such a deadly technology could be catastrophic in the wrong hands, be those of an enemy country, a terrorist group, or any civilian. These bullets would probably be very expensive to manufacture as well, so only a well-funded organization, like a state military, would be able to afford enough of these.
The feedforward construction of the control loop is sensible because the bullet needs to be able to adjust itself before it hits the target (or misses). In this case, the bullet’s position is the controlled variable, and it is manipulated by the orientation of its fins. The setpoint is the target, identified by a laser, apparently projected by the gun. It can be disturbed by weather conditions or a moving target. As long as the disturbances are small enough, this control scheme should work. It must be assumed that the bullet must aimed at least in the general area of the target upon firing. In addition, there must be a certain wind velocity or target displacement which is beyond the saturation range of control. Once these EXACTO bullets are designed to completion, a new project could focus on a range of products that would be optimized based on different conditions. For example, bullets intended to work well in high winds or for quickly-moving targets could be designed.
A controller possessing proportional-only action would be insufficient for this application. Shot accuracy is essential, so an offset in position would not work. Integral action would be very useful for this process because it considers the bullet’s progress along its path. The positional data gathered by the sensor would likely be noisy because of all of the potential disturbances. However, derivative action may be necessary because of the necessity for quick adjustments. A bullet travelling at 800 m/s has only so much time to adjust its position in the air. Tests would need to be run to determine if derivative action is too erratic in this case.
At this point, more work needs to be done to verify the usability of these bullets before bringing them onto the battlefield. Simultaneously, they have high potential for success, and it will be interesting to see how they develop. Whenever they become available for use, they will be very useful agents of death.
War seems to be an inevitable part of our society, so instead of hoping for world peace, making war less destructive and more efficient seems like the next best alternative. I think that the creation of a controlled destination bullet makes sense and could help save lives of many innocent bystanders on the battlefield if used appropriately. At the same time, I’m not entirely clear as to how it can be implemented. From the videos, the bullet seems to perform accordingly even with an untrained shooter, but I would like more clarity on how the feed forward system is regulating the bullet’s path.
This application hopes to limit the amount of casualties so by controlling flight path of the bullet based on specifications described by the shooter. Although the technology surrounding the bullet has not been disclosed, essentially it will have fins on the sides that will manipulate its shape based on the wind speed and the location of the person. However, I am confused as to how the bullet will be able to track the position of the moving target if it is working as a feed forward process. How are the specifications for the target made? How long will they take? How can they ensure that if a specification is made on a target that once the target moves the destination of the bullet is adjusting with the right target? Moving targets are probably the biggest disturbances that need to be accounted for during war. Unlike the videos shown on the blog, in a real life situation there will be many moving targets. A feedback system based on where the bullet is relative to where the target is an easier concept to grasp, but an impossible one to implement because that would require the opponents to wear some sort of sensor (doubt you will have many people volunteering for that option). A feed forward system is reactive and therefore not able to account for disturbances downstream. A feed forward system could be implemented to account for factors such as environmental conditions (such as wind speed, humidity, temperature, elevation above sea-level, air resistance, muzzle velocity, and gravity); however, a moving target is another issue. The time constants for the process have to be extremely small in order to get fast, precise responses. This can affect the robustness of the system.
Given the amount of disturbances and things that generally can go wrong in a war, I like the idea of a fail-safe option. This fail safe control will cause the bullet to self-destruct if it cannot hit the target. The bullet itself will have to be optimized to have maximum possible control before it can be used because although the fail safe system is great it will be costly if the bullet is consistently missing.
The type of controller that is absolutely necessary for this system is a PID controller. The time response has to be quick and stable, and the overshoot has to be limited to minimize the amount of offset (so that it doesn’t hit another target in the process). I think that the EXACTO bullet will be a beneficial system if implemented with the least amount of possible error.
First off, great job to the authors of this article. This was a lot of fun to read. Self-correcting sniper bullets sound like an idea from a movie. Oh wait, there was a movie about this called wanted but the characters in that movie were curving bullets coming out of a pistol which is even more impossible since it’s a smaller distance between the target and the shooter. I wonder if we will ever get that technologically advanced!
This is definitely a start. I think the general idea of have a laser directed control system is a brilliant idea. Before reading that I was trying to posit a solution to this to start with and I came up with a small thermal sensor on the tip of the bullet much like a heat seeking missile. This would probably work if you are in areas of cold climate but if the shooter is in the desert where the temperature outside is as hot as or hotter than that of a human body, it really wouldn’t work well. Using a laser to mark the target though seems much more useful in any situation I can think of and you could also probably mark a specific part of the body you want the bullet to converge on instead of just telling the bullet to head towards a certain heat signature.
The controller aspects relating to assignments of control and manipulated variables seem like they would make this as accurate as it could get with the plethora of possible disturbance variables. Right off the bat I can immediately posit that a proportional controller will not be useful for this application as the disturbances to this system can become very complex. It is very difficult to say whether or not the system controller should be comprised of a PI of a PID format. A PI controller would increase the response time of the bullet as opposed to a proportional controller so that is a benefit and makes me think that this would be the scheme to pick. It also probably has a larger operating range than a proportional controller. The part that I am conflicted with is the choice between a PI and a PID controller. Overall, a PID controller would respond faster than a PI controller because the derivative action responds fast to sudden changes that need to be made but I am sure when a bullet is shot and you have a three second window to control it, there is an enormous amount of noise and it is well known that derivative action does not handle noise well. For this reason I believe that a PI controller would probably be more stable with a small gain (kc) and small Tau (Ti). I think small parameters would allow it to make a large amount of tiny changes in short time intervals that would add up to the total curvature of the bullet into its target. I will end this comment by agreeing that adding a FF attachment to the controller would only add another level of accuracy and definitely improve the process. Again, Great Job!
This application makes total sense because it sounds like a very necessary product. The issue of stray bullets or inaccurate shootings is a very important issue in wars, since it leads to the accidental deaths of many. I can definitely envision myself using this product due to my love for high powered rifles with fascinating technologies and bullets that can change direction. I would also support this product because of its ability to cripple the effect of terrorism. Furthermore, this product can increase the accuracy at a shooting range as well as a sniper. It would also be possible to use by untrained shooters, which would be more helpful for beginners in order to prevent accidents. However, it would be much more effective to provide more details on how the feed forward system regulates the path of the bullet.
The controlled variable is the flight path of the bullet while the manipulated variable is the fin adjustment that controls the bullet path. This makes sense because the way that the fin is adjusted would allow for the bullet to travel in a different path. The disturbance variables mentioned of this process include wind speed or wind temperature. The process of controlling the effect of these disturbances makes logical sense; technologies within the process and on the bullets themselves would work to counteract these factors. However, the last sentence of the paragraph that discusses the control of the application does not make sense. It states that a control system would supposedly compensate for the factors by minimizing human error that arises from shooting at long distances. But it does not state which factors are being compensated. Would you be considering human error as disturbance factors? The next few paragraphs make more sense when talking about the disturbances monitored and how they would be incorporated into the system. The feed forward loop would monitor the disturbances in the path of the bullet in its flight and adjust its path to make sure that it is not affected by the wind factors.
The applications will require a controller aspect of some type, which may include a proportional integral controller. This seems like the only reasonable choice because of the following reasons. A proportional controller would have offset, which is insufficient for shot accuracy. The integral action would be useful since it considers the progress of the bullet; if added to a proportional controller, making a PI, it would increase the response time of the bullet. However, adding a derivative action controller would allow for a faster response but would introduce noise to the response. This would not be sufficient in a product such as this. The controller parameters can be tuned by starting with a low controller gain Kc and increase it with decreasing τi.
I found this article to be very interesting and had no idea that this type of technology was in the works. It seems mind blowing that in the time between firing and impact, the bullet could actually readjust its trajectory to create a more accurate shot. I have seen bombs that have similar technologies, with cameras or GPS tracking, to aim more accurately, but never imagined the same technology would be possible in a bullet. If these bullets prove to be effective, I have no doubt that they would be adapted, since they would give soldiers a huge advantage during conflicts. While expensive, the government would probably consider paying for this, knowing that it would help protect soldiers on the battlefield. I do have some questions as to whether or not the bullet would actually work. First, it seems unlikely that the electronics would be small and durable enough to fit inside the bullet and survive the initial explosion. I would expect the tiny wings to break off when exposed to the huge amount of force generated when the bullet is fired. I also do not know if the sensors would be accurate enough to measure the forces acting on the bullet midflight to the necessary degree. I suppose if the hardware was all worked out properly, though, this could be a very useful controls application.
As a possible change, it might be useful to add some sort of tracking function. Then instead of just going in a straight line regardless of wind gusts, the bullet would actually track a potentially moving target. Another possible change would just be to put the sensors and control system in the scope instead of the bullet. Instead of adjusting the bullet to hit where the scope is aimed, a control system could be used to calibrate the scope to view the spot where the bullet will hit.
As for the control system, I think feed forward is the appropriate scheme. There would probably not be enough time to react with a feedback system. Also, I think a PI would be the best option. The integral control would be very important to correct for a sustained drift in trajectory. The variables also make sense, as the only thing that really matters is where the bullet hits. The fin positions are an appropriate manipulated variable, since that is the only way of correcting the flight path. Wind speed is probably going to be the most important disturbance variable, I am not sure if temperature would have much of a noticeable effect on the bullet.
Personally, I love the product produced here. The EXACTO bullet will revolutionize the way modern day wars are fought. Having a bullet that is able to correct for misdirection and effect from winds will make snipers more accurate and less bullets will be required. There will be less missed shots and more successful missions. Also, snipers hitting their mark on the first shot instead of missing and needing to fire again will save the lives of many soldiers. I also believe that revolutionizing war weapons and making this extremely accurate and powerful will reduce the amount of war this war sees. It may turn into the cold war again, but if every nation has high-tech weapons, less people will feel inclined to fight one another. I would support this product that is produced by the DARPA for the safety and security of our armed forces.
Something that I might add to the development of this product is the reaction to rain. Air resistance and reaction to wind are good features since every bullet experiences effects from that. But, a lot of military operations or Special Ops are done in rainy conditions or in humid climates. Rain hitting a bullet in the air, over a long distance will increase drag, increase resistance and slow the bullet down. If there are fins on the bullet that allow the bullet to fly and change directions (or on large artillery shells), the fins could retract with the presence of rain to decrease drag and increase effectiveness.
I would suggest a PI controller for this product. A PI controller will produce a quick and fat response with little overshoot while ending up at the set point. A Proportional controller does not always reach the set point of the system, and that is not the response that is desired in this scenario. If the bullet does not reach its set point, then it will not hit its target. If it doesn’t hit its target, then all the technology that was put into the bullet was wasted time and money. We want the bullet to reach its target so the set point of the system must be reached. A PI controller will reduce the settling time and allow for the bullet to reach its set point, and reach its target trajectory, faster.
To increase the speed of this feed back process, it is possible to create a cascade feedback loop. The bullet will not be in the air very long since it is traveling at such high speeds. Since it will not be spending a lot of time in the air, we want the control system to react very fast and make sure the bullet is on target when it hits its mark. So a cascade loop with a PI controller would probably be the best control system for the EXACTO bullet.
Great project and great idea. This is a very real topic that will probably be a pivotal part of the new military tactics in years to come.